The principal objective of the Biostatistics Core will be to provide project investigators a centralized resource for biostatistics expertise. Statistical issues will be addressed at all levels of investigation: from the design of clinically based studies and laboratory experiments, to the maintenance of data quality; and from conclusions based on formal hypothesis testing, to important leads discovered by thorough data exploration. In support of this objective, the specific aims of the Core include: 1. Design: collaborate with project investigators in the design of laboratory experiments and clinical studies and the formulation of unambiguous hypotheses and hypothesis testing strategies. 2. Analysis: provide support for formal hypothesis tests in clinical and experimental data that ensure strong conclusions; statistical modeling and sensitivity analyses of prospective and retrospective studies; exploratory analyses that lead to further studies and experiments; and visual displays of data that clarify conclusions and uncover leads. 3. Data Quality Assurance: manage data and coordinate services with the Clinical Core A to ensure high quality, security and investigator accessibility for all clinical and experimental data. 4. Methods Research: Investigate new methodologies to directly address difficult data or design problems. RELEVANCE (See instructions): The Biostatistics Core will provide critical support for planning and design of experiments and clinically based studies, statistical analyses and display of data, and data management and integrity. This support is designed to ensure that studies yield reliable conclusions, resources are efficiently used, and exploratory analyses uncover important leads.